Novel protein acetyltransferase, Rv2170, modulates carbon and energy metabolism in Mycobacterium tuberculosis

Abstract

Recent data indicate that the metabolism of Mycobacterium tuberculosis (Mtb) inside its host cell is heavily dependent on cholesterol and fatty acids. Mtb exhibits a unique capacity to co-metabolize different carbon sources and the products from these substrates are compartmentalized metabolically. Isocitrate lies at one of the key nodes of carbon metabolism and can feed into either the glyoxylate shunt (via isocitrate lyase) or the TCA cycle (via isocitrate dehydrogenase (ICDH) activity) and we sought to better understand the regulation at this junction. An isocitrate lyase-deficient mutant of Mtb (Δicl1) exhibited a delayed growth phenotype in stearic acid (C18 fatty acid) media and we isolated rescue mutants that had lost this growth delay. We found that mutations in the gene rv2170 promoted Mtb replication under these conditions and rescued the growth delay in a Δicl1 background. The Mtb Rv2170 protein shows lysine acetyltransferase activity, which is capable of post-translationally modifying lysine residues of the ICDH protein leading to a reduction in its enzymatic activity. Our data show that contrary to most bacteria that regulate ICDH activity through phosphorylation, Mtb is capable of regulating ICDH activity by acetylation. This mechanism of regulation is similar to that utilized for mammalian mitochondrial ICDH.

Nα-Acetylation of the virulence factor EsxA is required for mycobacterial cytosolic translocation and virulence

“…While N α -acetylation in eukaryotes has been well studied, little is known about it in bacteria, including mycobacteria. Over 100 proteins in Mtb have been found to be N α -acetylated, including EsxA (32), and protein acetylation has been correlated to pathogenesis (33,34). Currently, three N α -acetyltransferases in E. coli, RimI, RimL and RimJ, have been identified to acetylate ribosomal proteins S18, L12 and S5, respectively (34)(35)(36).…”

“…Over 100 proteins in Mtb have been found to be N α -acetylated, including EsxA (32), and protein acetylation has been correlated to pathogenesis (33,34). Currently, three N α -acetyltransferases in E. coli, RimI, RimL and RimJ, have been identified to acetylate ribosomal proteins S18, L12 and S5, respectively (34)(35)(36). A biochemical study has found RimI in Mtb has a relaxed substrate specificity, but little is known about the physiological substrates of the enzyme (37), which warrants further investigation.…”

More than cholesterol catabolism: regulatory vulnerabilities in Mycobacterium tuberculosis

“…Rv2170 is a protein acetyltransferase with the ability to acetylate, succinylate, and propionylate isocitrate dehydrogenase (Icd1/Rv3339c). As with the modification of other metabolic enzymes, acetylation of Icd1 reduces isocitrate dehydrogenase activity and shifts fatty acid metabolism toward the glyoxylate cycle and reduces flux through the TCA cycle [28]. Acetylation of isocitrate lyase (Icl) has varying effects on enzymatic activity and protein stability depending on the site of the modification [29].…”

“…A succinyltransferase has not been definitively identified. Mt Pat and Rv2170 [28] may catalyze succinylation in addition to acetylation and/or propionylation. Rv0802c, a GCN5-related N-acetyltransferase (GNAT) family member, co-crystallizes with succinyl-CoA suggesting that Rv0802c catalyzes succinylation of lysines [35].…”

Mechanisms, Detection, and Relevance of Protein Acetylation in Prokaryotes

“…Previously, the M. tuberculosis Rv2170 KAT protein was found to acetylate key lysines on isocitrate dehydrogenase (ICDH), which results in a reduction of ICDH activity (87). Other identified type IV KATs include Porphyromonas gingivalis Pat (88), Bacillus subtilis AcuA (89), Saccharopolyspora erythraea SacAcuA (90), Rhodopseudomonas palustris RpKatA (71), Sulfolobus solfataricus Pat (91, 92), and S.…”